Oils of high viscosity index and process of making the same



Patented July 11, 1939 PATENTS OFFICE olLs OF HIGH vIscosrrY INDEX ANDPROCESS OF MAKINGTHE- SAMIE James M. Whiteley, Roselle, N. J., assignor'to Standard Oil Development Company, a corporation of Delaware NoDrawing. Application August 23, 1935,

' Serial No. 375529 4 Claims.

The present invention relates to processes for making oils of high;viscosity and of high viscosity index from crude petroleum oils whichhave hitherto been considered unsuitable for making such oils, and itrelates more particularly to the manufacture of gear oils of highviscosities and high viscosity index,'such as are suitable for theefficient lubrication of machinery requiring lubricants of this type.

10 .The term viscosity index, which herein will bedesignated by'thecommonly used abbreviation V I.,'gives an indication of the extent towhich an oil will retain itsbody, or viscosity, when the oil issubjected to considerable changes in temperatures, such as those towhich crank-case and transmission oils for automobiles and othermachinery are subjected.

j Much consideration has been given to the production of crank-case oilsfor automobile engines,

2 and oils of'high V. I. have been manufactured for this purpose and areavailable. The V. I. of

, transmission oils has received less consideration than the V. I. ofcrank-case oils. However, the starting characteristics of transmissionoils at low temperatures are as important as those of the crank-caseoils; Ease of gear shifting depends on the V. I. of the oils and thelack of the necessary V. I. will become noticeable to thedriver of a carby the difliculty of shifting gears during cold Weather.

A low V. I. transmission oil is not safe for operation in climates wherethe temperature varies widely. When the weather is hot the viscosity ofthe oil may become too low for adequate lubrication and in cold weatherthe oil may become so viscous that it will not flow but will channel andnot supply suflicient lubrication to the transmission gears. For thesereasons high V. I. oils should be used in transmissions of automobilessince these oils are frequently not changed from season to season. i

In accordance with the present invention, improved oils of the kindreferred to are obtained at low cost, based on the utilization ofdistilla- 45 tion residues heretofore not considered suitable for thisuse.

When a given crude petroleum oil is fractionated by distillation, thefractions which distill over generally have a uniform V. I. which does Fnot vary much over 10 points, but this V. I. depends on the source ofthe crude oil which is distilled. However, the V. I. of thestill-bottoms changes with the extent of the fractionation, especiallyunder refinery conditions where some cracking takes place. When the oilwhich is left in the bottom has a viscosity of about 150 seconds Sayboltat 210 F. (after removal of wax, asphalt, and the like), its V. I. isstill similar to that of 'the oil which distills over.

In the present invention, the viscosity is in- 5 creased byfurtherdistillation, preferably with mild cracking. The oil (asdistinguished from wax, asphalt, and other extraneous material) in thebottoms from all crudes appears to approach the samevisc'osity, namely,about 2,000 Saybolt at 210 F. Thisprobably occurs because all of theunstable hydrocarbons-are cracked, the cracked products distill over,and the fractions of lower V. I. are sufiiciently volatile to distillout or are removed as asphalt in the process of decolorizing the oil.The resulting bottoms-oil is of a uniform character and blends withother oils as if it had a V. I. of around 120. Hence, when it is blendedin equal volumes with an oil of 44 viscosity Saybolt at 210 F. andhaving a v. I. of 100, the blend will have a V. I. of about 113.

This high V. I. oil may be recovered from the crude bottoms-oil inseveral different ways. It may be obtained in purified formfromvacuumstill, steam-still or flash-coil bottoms by any of the severalwell known solvent, de-asphalting and/or,dewaxingprocesses. It may alsobe Oh? 'taineddirectly by dewaxing and decolorizing the crude stillbottoms by clay or acid treatment, and then fractio'nating these, eitherby distillation or by solvent precipitation or'other suitable means. Theimportant result is, that when the heaviest portion is finally obtainedfree of asphalt and wax, it blends with other oils as if it had a highV. I.

For example, Pennsylvania bright stock of 150 Saybolt viscosity at 210F., generally known as FFF valve oil, may be reduced still further to a10% bottoms-oil by steam or vacuum distillation at a temperature of upto about 750 F. The bot- 4.0 toms-oil will then have a viscosity ofabout'1200. Saybolt at 210 F. If this bottoms-oil be blended with a 100V. I. oil of lower viscosity than the overhead oil, the resulting blendwill have a V. I.

of above 100, for instance 115 V. I. The character of the resultingblend will depend upon the vis-' cosity of the light oil blended and theV. I. required.

The bottoms stock, reduced as previously described, may be used tothicken light oils of above 100 V. I. and to increase the V. I. of evenhigh V. I. oils. These light oils may be synthetic oils, such as thoseprepared by the aluminum chloride synthesis of unsaturated hydrocarbonsfrom cracked wax or from other sources. These light oils may also beprepared by the solvent extraction of high V. I. overhead oil, such asPennsylvania stock of 42 to Saybolt viscosity at 210 F.

By blending the heavy bottoms with what may be called super-V. I.neutral oils, made by selective solvent extraction of Pennsylvaniadistillates, it is possible to prepare what are believed to be thehighest V. I. mineral oils ever made from petroleum oils.

The oils blended with the heavy bottoms-oil may also be of the glyceridetype, such as palm, olive, sperm or rape-seed oils. Blends of thepurified oil from the crude bottoms. with these oils will haveviscosity-temperature characteristics depending upon the nature of thelight oil used in the blends. Thus it is possible to make a transmissionoil of 250 Saybolt viscosity at 210 F. and with a V. I. of 120. Thistransmission oil has good load-bearing qualities as well as high V. I.and its viscosity does. not break down during use. For example, a goodgrade of high V. I. bottoms-oil suitable for blending with light oils toobtain oils with a high V. I. has been prepared from a Palembang crudeoil by the extraction of the heavy pitch bottoms, from a pipe-stilloperation, by means of light hydrocarbons, such as liquid propane orbutane.

The effect of the addition of an oil of 1375 viscosity, SayboltUniversal at 210 F., recovered from. Palembang pipe-still bottoms byextraction with light hydrocarbons and dewaxing is shown by thefollowing examples:

Inspection of the oil made from Palembang crude oil gave the followingresults:

A. P. I. gravity degrees 16.5 Viscosity at 210 F seconds Saybolt 13'7bPour F. (viscosity pour) Conradson carbon -2 per cent 4.92

The viscosity of the above oil made from Palembang crude, at 85 F., isso high that the oil seems to be solid at the conditions of the A. S. T.M. pour test, being near 2,000,000 seconds at 85 F. The oil will flow at85 F. if given sufficient time.

Hitherto, the main source of high V. I. oils has been chieflyPennsylvania and some other paraffinic crude oils of which there hasbeen a limited supply. The present invention makes it possible toproduce high quality, high V. I. lubricating oils from other crude oilswhich are more abundant and less costly and to conserve the limitedsupply of natural crude oils from which high V. I. oils are now made.

The foregoing description is illustrative only and various alternativemethods and compositions may be used within the scope of the appendedclaims, in which it is intended to include all novelty inherent in theinvention as broadly as the prior art permits.

I claim:

1. The process of preparing residual petroleum lubricating oil of highviscosity and high viscosity index from crude oil residual stocks,comprising distilling therefrom under mild cracking conditions, thelower viscosity oil fractions and the cracked fractions produced duringthe distillation until the residual oil, when freed from asphalt andwax, reaches a viscosity considerably in excess of seconds Saybolt at210 F., and separating waxy and asphaltic constituents from theundistilled V residue.

2. A process according to claim 1 in which the distillation is continueduntil the viscosity of the residual oil freed from wax, asphalt andother extraneous substances approach 2,000 seconds Saybolt at 210 F.,and thereafter wax and asphalt are removed.

3. A process according'to claim 1 in which the residual is reduced toviscosity of the order of about 1200 secs. Saybolt at 210 F. or higher.

4. A process for preparing an improved lubricating' oil, comprisingdistilling a crude oil residue under mild cracking conditions wherebythe constituents of lower viscosity index are cracked and removed asvapor, continuing distillation until the viscosity of the residue is ofthe order of 1200 to 2000 secondsSaybolt at 210 F., separating the waxand asphalt from said residual. then blending this residue with alighter oil to increase the viscosity and viscosity index of the same.

'JAMES M. WHITELEY.

